Isolation of a cDNA encoding a beta-1,4-endoglucanase in the root-knot nematode Meloidogyne incognita and expression analysis during plant parasitism

A beta-1,4-endoglucanase encoding cDNA (EGases, E.C. 3.2.1.4), named Mi-eng -1, was cloned from Meloidogyne incognita second-stage juveniles (J2). The deduced amino acid sequence contains a catalytic domain and a cellulose-bin ding domain separated by a linker. In M. incognita, the gene is transcribed in the migratory J2, in males, and in the sedentary adult females. In pre- parasitic J2, endoglucanase transcripts are located in the cytoplasm of the subventral esophageal glands. The presence of beta-1,4-endoglucanase trans cripts in adult females could be related, to the expression of the gene in esophageal glands at this stage. However, cellulase activity within the egg matrix of adult females suggests that the endoglucanase may also be synthe sized in the rectal glands and involved in the extrusion of the eggs onto t he root surface. The maximum identity of the predicted MI-ENG-1 catalytic d omain with the recently cloned cyst nematode beta-1,4-endoglucanases is 52. 5%. In contrast to cyst nematodes, M. incognita preparasitic J2 were not fo und to express a beta-1,4-endoglucanase devoid of a cellulose-binding domai n.